2.8 THE COSMOS CONVERTER Z88G

Sometimes 3D CAD programs include so-called automeshers which devide a CAD model into finite elements. This generated mesh can be stored in some output format to fit the needs of the various FEA programs. But often, these automeshed FEA structures feature very bad nodal numberings. To improve the nodal numbering, see the Cuthill- McKee program Z88H.

One of this output formats is the COSMOS format for the COSMOS FEA program.

Z88G is developed and tested for Pro/ENGINEER by Parametric Technology. USA. Pro/ENGINEER must include the option Pro/MESH. Be sure to define the material data (e.g. for steel, only Young's Modulus and Poisson's Ratio is really needed) in Pro/ENGINEER.

Then you may activate FEM in the Pro/ENGINEER program after designing your 3D model , define a coordinate system (which must be in harmony with Z88 !) and add forces and boundary conditions to single points. Create these single points with Feature > Datum > Point. In most cases, surfaces are possible, too.

Modify the mesh control values, if necessary. Create the mesh with Make Model and choose the element type e.g. Tet Mesh or Shell Mesh. Store the mesh with Output Model, choose COSMOS/M and linear or parabolic. Enter z88g.cos for the output file name.

Then lauch the converter Z88G. The converter produces the Z88 input files Z88I1.TXT, Z88I2.TXT and Z88I3.TXT automatically. You may then enter the Z88 input files and edit values e.g. material data and integration orders, if necessary.

Test the Z88 input files generated by Z88G with the filechecker Z88V. Plot Z88I1.TXT with the plot program Z88P. If you find a 3D model totally flat: You defined a coordinate system CS0 in Pro/ENGINEER which does not fit Z88's needs. Simply define a new correct coordinate system in Pro/ENGINEER and define it as datum when outputting the model.

You may create the following Z88 element types with Z88G:

Tetrahedron No.16 (Tetrahedron, parabolic in Pro/ENGINEER)

Tetrahedron No.17 (Tetrahedron, linear in Pro/ENGINEER)

Plane stress No.14 (Shell, triangle, parabolic in Pro/ENGINEER)

Plane stress No.7 (Shell,quadrangle, parabolic in Pro/ENGINEER)

Plate No.18 (Shell, triangle, parabolic in Pro/ENGINEER)

Plate No.20 (Shell,quadrangle, parabolic in Pro/ENGINEER)

Pro/ENGINEER makes no distinction between plane stress elements and plate elements, so, it's up to you to feed Z88G with the right information; choose the proper element type in Z88G before starting the conversation run:

(Before running the conversation choose the right type of elements; works similar for the UNIX version of Z88G in console mode)

Z88G looks quite harmless, but proper operated Z88G is a mighty tool which allows you to give very large FEA structures to Z88.